This invention relates to structures for connecting together a plurality of frame bars at their ends and a method of producing such structures.
For connecting together elongated construction materials such as frame bars at their ends, it has been known, as shown in FIG. 10, to attach an L-shaped metal bracket 31 on the surface of each frame bar 3, leaving an end surface 3a of one of them exposed to the exterior. Frame bars thus connected, however, are unsightly because the metal brackets used to connect them together protrude from their side surfaces. Such metal brackets, as well as screws which are used to attach them to the frame bars, can be a source of serious accidents because they can easily catch a part of the worker's clothes.
It is therefore an object of this invention to eliminate such problems of the prior art technology and to provide safe connector structures which do not have any externally protruding parts and can be attached to frame bars securely and easily.
It is another object of this invention to provide methods of producing such connector structures efficiently.